Catalytic hydrogenation of nitriles, dinitriles to amines, diamines
Nbsp; Kazakh National University of al-Farabi Допущен к защите: Зав.кафедрой физической химии, катализа и нефтехимии д.х.н., профессор М. К. Алдабергенов « » май 2014 г.
Graduation work
«Studying of influence of hydrogen pressure and temperature on hydration of acetonitrile»
speciality 05072100 – «Chemical Technology of Organic Substances»
Выполнил,
студент 4 курса M.M.Shangdyev
Научный руководитель
д.х.н., асс. профессорТ. С. Абильдин
Нормокогтролер
Almaty 2018
Essay
Graduation work contains: 43?с., 1 schemes, 4 figures, 2 tables, 85 sources of literature.
Key words: hydartion, nitrile, amine, catalyst, ammonia, alcohol, pressure, hydrogen, mechanism.
The object of the study is acetonitrile,ethylamine Ni-Nbск(5%Nb) -catalyst.
Aim of the work - a study of the effect of hydrogen pressure and temperature on the rate of reaction and the yield of ethylamine in the hydrogenation of acetonitrile in the presence of a Ni-Nb (5% Nb) catalyst in the liquid phase.
In the course of the work, experimental studies of the kinetic patterns of hydrogenation of acetonitrile were carried out, varying the experimental condition.
THE LIST OF MAIN ABBREVIATIONS
KIHP – The kinetic installation for high pressure
GLS - gas-liquid chromatography
IR Spectra- infrared spectroscopy
Ме-Н–methal-hydrogen
Н-5 – Ni-Nb (5 %Nb)
Т, К – temperature(Kelvin)
°С – Celsius degree
С – concentration
– hydrogen pressure ,MPa
– hydrogen overpressure
CONTENT
INTRODUCTION
Aliphatic and aromatic amines and their derivatives are widely used for the synthesis of polyamide fibers and heat-resistant plastic materials, biologically active substances, pharmaceuticals, effective surfactants, synthetic dyes, etc., which makes the problem of developing convenient and economically viable methods for their preparation extremely urgent.
The Republic of Kazakhstan is traditionally considered as the exporter of raw materials, primarily -oil and gas. In Kazakhstan, there is an acute shortage of amines in various structures.
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The reaction of oxidative ammonolysis, developed in our country, opens wide opportunities for the synthesis of nitriles of various structures.
A promising and affordable method for the synthesis of aliphatic and aromatic mono-, diamines is the hydrogenation of the corresponding mono-, dinitriles, where the products of deep processing of oil and coal can be used.
Aim of the work -a study of the effect of hydrogen pressure and temperature on the rate of reaction and the yield of ethylamine in the hydrogenation of acetonitrile in the presence of a Ni-Nb (5% Nb) catalyst in the liquid phase.
Tasks:
1) Study of the process of catalytic hydrogenation of acetonitrile to ethylamine in the presence of a modified catalyst "H-5" -Ni-Nbsk (5% Nb) under the hydrogen pressure in the liquid phase.
2) Study of the kinetics of hydrogenation of acetonitrile-ethylamine at
various hydrogen pressures and temperatures on a Ni-Nbsk (5% Nb) catalyst.
Scientific novelty -for the first time, the kinetic mechanisms of the hydrogenation of benzonitrile to benzylamine in the liquid phase are determined with a wide variation of condition of the experiment (T, PH2, etc.).
Practical significance- The practical value of the work is to establish optimal parameters for carrying out the process of hydrogenation of acetonitrile to ethylamine in the liquid phase.
LITERATURE REVIEW
Catalytic hydrogenation of nitriles, dinitriles to amines, diamines
The study of the kinetics and mechanism of hydrogenation of nitriles and dinitriles is of considerable theoretical and practical interest in connection with the increasing use of various amines in industry /2/.
Amines can be obtained in various ways. The most convenient and common method is the catalytic hydrogenation of the corresponding nitriles. In the synthesis of primary amines by catalytic reduction of nitriles, side reactions occur leading to the formation of aldehydes, Schiff bases, secondary and tertiary amines, amides, amines, carbonyl compounds and other condensation products /1-6/.
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The reaction can be represented by the general scheme:
The primary amine with imine gives Schiff's base or the addition product:
which, by attaching hydrogen, give a secondary amine:
It is also possible for the secondary amine to react with imine:
which forms tertiary amine when hydrogenated
The metals of the eighth group: palladium, platinum oxide promoted, nickel and cobalt, skeletal, nickel and cobalt catalysts on supports, nickel and cobalt-boron contacts prepared by reducing the metal from an aqueous solution of its salt with sodium borohydride-are used as catalysts for the reduction of nitriles, dinitriles.
/2-7/.
The activity of catalysts in the hydrogenation of nitriles decreases in the series:
Pt, Pd>Ni, promoted by titanium or Cr>Ni>Co>Fe,Сu.
Generally, the reaction is carried out in a liquid phase in an ammonia or inert solvent (alcohol, dioxane) saturated with ammonia /1-8/.
More selective catalysts in the synthesis of aminonitriles are palladium and platinum on aluminum oxide, as well as nickel- and cobalt- boride contacts modified with chromium additives /7,9/. On these catalysts, the uptake of hydrogen spontaneously ceases, despite the fact that a significant portion of the reacted dinitrile has not yet reacted. Moreover, it was shown that when the concentration of dinitrile decreases, further hydrogenation is strongly slowed down due to adsorption displacement from the surface of the catalyst by the resulting aminonitrile.
The literature data on the catalytic reduction of dinitriles of carboxylic acids are few and presented mainly by patents. An exception is adipic acid of dinitrile, the hydrogenation of which into industrially important hexamethylenediamine has been extensively studied /4,10-14/.
It is known from the literature (1-8,10-13,15) that the first intermediate compound formed on the catalyst surface during the hydrogenation of dinitriles is aldimine:
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dinitrile aldimine aminonitrile
aldimine diamine
The formation of aminonitrile in the catalytic hydrogenation of aromatic dinitriles indicates a non-simultaneous reduction of nitrile groups /1,4,6,7,9-13,16,17/.
The effect of the addition of ammonia on the composition of hydrogenation products of nitriles and dinitriles is consistent with the scheme proposed by the authors /1-7, 15-18/, where there is supposed interaction of the intermediate forming aldimine with ammonia , leading ultimately to an increase in the yield of primary amines, diamines:
The direction of catalytic hydrogenation of nitriles depends on their structure.
Dinitrile- and p-phthalic acids are hydrogenated respectively to m- and p-xylylenediamines /4, 6, 16, 17/, for example from terephthalonitrile in the presence of ammonia in lower aliphatic alcohols, is synthesized p-xylylenediamine with 97-98% yield in scheme shown below / 16, 17 /
+Н2 (I)
terephthalonitrile aldimine 4-cyanobenzylamine
+NH3
-NH3
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+ Н2 (II)
4-cyanobenzylamine aldimine xylylenediamine
+NH3
-NH3
It was shown in [16, 17] that the hydrogenation of terephthalonitrile proceeds with a decreasing speed, the calculated amount of hydrogen is absorbed. Hydrogenation begins at a very high rate before the absorption of two moles of hydrogen per mole of dinitrile , after which the rate of hydrogen uptake is somewhat reduced, the subsequent two moles of hydrogen are slowly added. A characteristic feature of the kinetics of hydrogenation of isophthalonitrile is a constant decrease in the reaction rate throughout the experiment.
The results of the study using different methods for analyzing the products of the catalytic reduction reaction of isophthalonitrile indicate that [16, 17] that under the selected conditions, only one of the nitrile groups of terephthalonitrile is predominantly hydrogenated in the first reaction stage, resulting in the formation of 4-cyanobenzylamine. Only after reduction of the nitrile group of 4-cyanobenzylamine can p-xylylenediamine be obtained in quantitative yield.
Dinitrile phthalic acid is hydrogenated exclusively to the cyclic amine:
Sokolsky D.V. with colleagues (5, 19) studied the hydrogenation of acetonitrile, acrylonitrile, stearic and oleic acid nitriles on skeleton nickel and nickel-titanium catalysts in alcohol and 0.1 N NaOH under hydrogen pressure in the presence of ammonia and without ammonia. They found that the rate of hydrogenation of nitriles and the yield of amines are largely determined by the nature of nitriles, catalyst and solvent. The influence of ammonia, the temperature of the test and the pressure of hydrogen on the rate of hydrogenation of the nitriles studied and on the composition of the reaction products was especially noted. When hydrogenating nitriles, Ni-Ti-the catalyst proved to be more active than Niск. The nitriles studied for reducing the reactivity under similar conditions are located in the following sequence:
acetonitrile> acrylonitrile> oleonitrile> stearonitrile
In the hydrogenation of acetonitrile in alkali (5, 19), the specific activity of the nickel-titanium catalyst is 2-4 times, and in alcohol 7-10 times higher than that of skeletal nickel. It was found that the introduction of titanium into the nickel-aluminum alloy (5.20) promotes the adsorption of amines from the surface of the catalyst by nitriles, i.e. on promoted catalysts (Ni-Ti, Ni-Co), nitrile adsorbs better than amines, which naturally leads to an increase in the rate of hydrogenation of nitriles on these catalysts. An increase in the catalytic properties of the skeleton, nickel titanium-promoted catalyst is associated with the formation of a TiO2 structural promoter upon the destruction of TiAl3 by alkali. In the leaching of aluminum, the crystal lattice of the alloy is rearranged into a cubic face-centered lattice with parameters 3.52-3.53 A / 20 /.
The authors of [20] believe that the expansion of the crystal lattice of nickel with a cubic face-centered structure after leaching of the alloy with titanium is associated with the introduction of a certain amount of titanium into the crystal lattice or with the increase in the amount of absorbed hydrogen by the nickel lattice.
Kindler and Hess proposed the formation of secondary and tertiary amines during the hydrogenation of nitriles in aqueous and anhydrous media in schemes A and B / 4, 17, 32 /:
Scheme A
Scheme B
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